In order to determine a fill level of a viscous, granular or coarse-grained filling material or bulk material (referred to as “filling material” hereinafter), it is advantageous to record the shape of the surface of the filling material. Since the surface of the filling material may be uneven and may comprise hollow troughs or bulk peaks for example, this information is important for being able to accurately determine the actual fill level or the mass of the filling material.
The information regarding the topology of the surface of the material to be monitored can also be advantageous in the field of object monitoring or mass flow detection.
Fill level measurement devices of this type can be designed to determine the surface topology of the filling material by scanning the surface, either by means of digital beamforming or by mechanically adjusting the main emission axis of the duplexer of the fill level measurement device. For accurate calculation of the surface topology, the evaluation unit of the fill level measurement device has to know the direction of the main emission axis of the duplexer of the fill level measurement device at all times during the measurement. However, it has been found that even with the exact knowledge regarding the direction of the main emission axis, the calculation of the surface topology of the filling material can be inaccurate.